In situations of localized disease it may be difficult or impractical for physicians to extricate assay samples or perform tests specifically defining pathologic status at given lesions. Inflammatory sites of periodontal lesions are a representative problem. Our objective is to develop a bioprobe-assay system useful in the diagnosis and evaluation of periodontal disease. The specific aim is to create a probe for the periodontopathogen Actinobacillus actinomycetemcomitans (Aa). The assay system will utilize a small probe coated with antibody to Aa microbes, which when placed at an infected site will bind specifically Aa organisms. Bound Aa will be immunologically processed in vitro to produce an optical signal quantitatively related to the number of Aa at the lesion. The assay will be rapid and simple, suitable for general office practice. In contrast to current methods it will yield objective measures which aid in diagnosis and evaluation of activity within lesions; thus enabling physicians to provide better health care. Phase I research focuses on development and characterization of the assay system. Its correlatability with clinical diagnosis will be examined in Phase II. The system has multi-application potential using similar probes with antibodies to other entities.